Traditional electrophotographic (EP) devices have a spinning polygon mirror that directs a laser beam to a photoconductor, such as a drum, to create one or more scan lines of a latent to-be-printed image. Recently, however, it has been suggested that torsion oscillator or resonant galvanometer structures can replace the traditional spinning polygon mirror and create scan lines in both the forward and reverse directions (e.g., bi-directionally), thereby increasing efficiency of the EP device. Because of their MEMS scale size and fabrication techniques, the structures are also fairly suggested to reduce the relative cost of manufacturing. Unfortunately, scanning in two directions adds a measure of complexity to image referencing since reference points need occur for each of the forward and reverse scans at opposite ends of the printed page and the slightest of deviations amplifies print image imperfections. Delays in reference sensors further complicate the process.
Also, any asymmetry in the motion of the oscillator or galvanometer results in errors in print linearity and line-to-line registration across the printing area. In this regard, there is first a notable drawback in the discontinuous nature by which forces are applied to the galvanometer or oscillator and asymmetric distortion of laser scanning motion can be introduced if left uncontrolled. Second, since the mechanical properties of the constituent materials that compose the galvanometer or oscillator are influenced by temperature, and the damping of the motion is dependent on air density (in turn, a result of both temperature and pressure, where pressure varies with altitude, for instance), it is clear that ambient operating conditions affect the shape and magnitude of the linearity and misalignment of scan lines. Thus, print quality changes occur as a result of changes in operating altitude, temperature or from occurrences of severe weather, for example.
Accordingly, there exists a need in the art for characterizing the manner in which bi-directionally scanning EP devices should operate according to various component characteristics and operating conditions. Particularly, there are needs by which knowing the actual characteristics and operating conditions of the EP device will relate to making corrections to improve print quality, such as aligning forward and reverse bi-directional scan lines. Ultimately, the need extends to efficaciously retaining the information so that it can be easily retrieved to implement the print quality corrections. Naturally, any improvements should further contemplate good engineering practices, such as relative inexpensiveness, stability, low complexity, ease of implementation, etc.